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Power Line Circuits
Last Updated on:
Saturday, April 26, 2008 07:18 AM |
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| Circuits Designed by Dave Johnson, P.E. : |
- UNPLUGGED POWER CORD ALARM
Many medical devices, such a portable X-ray and ultrasound equipment, carry their own batteries. However, the frantic pace of some hospital
emergency rooms might cause the device to be shoved off into a corner without being plugged back into an AC power source to recharge their
batteries. So, I designed this circuit to emit an audible alarm whenever the device’s power cord was unplugged from the wall for a period of
time. The device was designed to snap onto the outside of a power cord, where it senses the AC electric field emitted. No direct connection to
the internal wires of the power cord is needed. I also included a low battery voltage monitor.
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- ISOLATED AC CURRENT MONITOR
This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary
winding. The transformer contains a single turn primary with a low 0.001-ohm resistance. It can easily handle 30 amps of AC current
and provides at least 500vac of isolation. With the components shown, the output AC voltage is scaled so 1 amp of current produces 100mv
of AC voltage.
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| Links to electronic schematics, circuits, designs and/or diagrams for engineers,
hobbyists, students & inventors: |
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3˝ Digit DVM IC Measures Power Factor: 04/28/94
EDN-Design Ideas / (added 09/05) The circuitry in Fig 1 allows the ICL7106/7107 digital-voltmeter IC, IC4, to measure power factor to 0.1%
resolution and operate from a single 9Vdc supply. An important feature of the circuit is that variations in load current, line voltage, and
line frequency do not affect measurements. For inductive loads, power-factor measurements are accurate to 1% in the range of 0.85 to 1. |
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AN-872: TP3420A Line Interface Circuit Considerations: National
Semiconductor - Application Note (Circuit / schematic design added 6/06) |
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Calculating Power Dissipation for Differential Line Drivers: National
Semiconductor - Application Note (added 2/06) |
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Off Line Power Supply Requires Few Parts: 02/17/94 EDN-Design Ideas /
(Electronic Circuit diagram added 03/03) -This simple non-isolated off-line power supply can provide up to150 mA5V and uses only a handful of
components from110-230-Volt AC input voltage. Note that the low voltage output is directly connected to the mains; it cannot be used when the
low voltage part can be touched. |
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